Characterization and Control of Structure, Energetics and Electrical Properties at Interfaces between Perovskite Active Layers and Charge-Collection Electrodes

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Nontechnical Description: This project focuses on the characterization and control of the interfaces formed between electrodes and new materials (perovskites) that have shown great promise as active layers in new solar cell platforms. Such platforms have potential as inexpensive, earth-abundant alternatives for production of electricity from sunlight. One of the key challenges in the development of new energy conversion platforms is the understanding and optimization of the transfer of electrical charges between the active layer material and the electrical contacts. This project develops new measurement approaches in order to understand the structure of the active layer near the electrical contact, and how this structure influences electrical properties that ultimately control energy conversion efficiency. The project also provides opportunities for training of graduate students at the University of Arizona and for undergraduate students from the AZ Science, Engineering, and Math Scholars (ASEMS) Program, which focuses on students from minority populations, low-income households, and families where the student is the first to attend college. The co-principal investigators also continue a partnership with Yavapai Community College in Prescott, Arizona - providing "gateway" research experiences for freshman and sophomores.Technical Description: This project focuses on the nanometer-scale characterization and control of physical, energetic and electrical property heterogeneity, across interfaces between metal halide perovskites, as well as hybrid active layer materials, and electrical contacts. These interfaces are model systems to explore charge collection or injection in emerging thin-film solar energy conversion platforms. The project includes: a) control of interface composition in prototype electrical contacts and charge selective interlayers, using self-assembled monolayers with terminal functional groups that "template" growth of perovskite active layers; b) characterization of valence band energies and energetic dispersion as a function of active layer structure via high-sensitivity UV-photoemission spectroscopies and high-resolution, angle-resolved X-ray photoemission; c) probing conduction band energies in the active layer and dispersion in band edge energies arising from compositional and structural heterogeneity, using waveguide-based spectroelectrochemical techniques; d) characterization of the electrical properties of contact/active layer heterojunctions at 10-100 nm length scales using conducting-tip atomic force microscopy to map heterogeneity in electrical properties. This fundamental study could reveal the charge transfer mechanisms and ultimately lead to efficient energy conversion in the emerging solar cell platforms.